A seat reclining apparatus of this kind comprises a pair of base plates on the outer side and on the inner side fixedly mounted respectively on the left- and right-sides of a seat cushion, and a pair of arms fixedly mounted respectively on both left- and right-hand sides of a seat back and mounted respectively on the base plates. The seat reclining apparatus further comprises a pair of locking mechanisms which comprise a pair of upper teeth mounted respectively on the arms, a pair of lower teeth engageable with and disengageable from the upper teeth, respectively, and a pair of cam members for operating the lower teeth, respectively. The arrangement is such that the cam members operate by operation of an operating lever which is mounted on one of the base plates.
The arrangement is such that, by operation of the operating lever which is arranged on the base plate on, for example, the outer side, the locking mechanism of the seat reclining unit on the inner side follows in interlocking relation to the locking mechanism of the seat reclining unit on the outer side, so that locking and unlocking of the lower teeth with respect respective to the upper teeth are executed. As this interlocking arrangement, an actuating lever on the outer side, which is arranged at a rear portion of the base plate on the outer side and which is interlocked with the operating lever, and an actuating lever on the inner side, which is arranged at a rear portion of the base plate on the inner side, are connected to each other by a wire which is so, arranged as to wind a front section of the seat.
However, in the above-described conventional seat reclining apparatus, there is a case where shift in phase at locking occurs between the seat reclining units on the outer side and on the inner side, due to distortion of a seat frame, distortion of a floor of a vehicle body, and the like, whereby, even if, for example, the seat reclining unit on the outer side is locked, the seat reclining unit on the inner side is brought to imperfect or incomplete locking, that is, so-called half locking. In order to prevent breakage of the upper tooth, the lower tooth and the like due to this half locking, the conventional seat reclining apparatus is arranged such that thickness of each of the upper tooth, the lower tooth and the like increases to raise strength thereof. For this reason, there is a problem that weight increases and a cost is raised.
Further, by variation in dimension of various parts of the seat reclining units on the outer side and on the inner side, and the like, there is a case where shift in phase occurs between the seat reclining units on the outer side and on the inner side at unlocking so that unlocking of the seat reclining unit on the outer side and unlocking of the seat reclining unit on the inner side are not synchronized with each other. For this reason, there is a fear that operating feeling of the operating lever is reduced.
Furthermore, the wire is arranged so as to extend from the rear portion of the base plate on the outer side to the rear portion of the base plate on the inner side through the front portion of the seat. In such wire arranging method, the wire is inevitably lengthened. For this reason, there is a problem that pulling or tension efficiency of the wire is reduced so that operability of the operating lever is deteriorated, and a cost increases.
Moreover, recently, reduction in weight of the vehicle has strongly been desired and, in keeping therewith, plate members such as the base plates and the like use plates thin as far as possible. Since, however, a considerably large load from the seat back through the arms is applied to various pivots of the seat reclining apparatus, i.e., pivots for the upper teeth, it is required to fixedly mount these pivots firmly on the base plates. For this reason, it was impossible to reduce the thickness of each of the base plates to a value equal or smaller than a predetermined thickness.
Further, since the pivots for the upper seats are important for supporting the seat cushion, the pivots are fixedly mounted by welding because the base plate is thin in thickness, or are caulked to pivot mounting portions in which washers are welded to the pivots to increase the thickness thereof. Since welding operation is executed in this manner, a welding step is required in addition to an assembling step. For this reason, there was a problem that automatizatlon of the assembling is made impossible, and a manufacturing cost increases.
This invention has been done in order to solve the above-discussed problems of the prior art, and an object of the invention is to provide a seat reclining apparatus capable of correcting shift in phase at locking and unlocking of a pair of seat reclining units which are arranged respectively on both left- and right-sides of a seat.
Mother object of this invention is to provide a seat reclining apparatus in which, in an interlocking arrangement of a pair of seat reclining units on the outer side and on the inner side, a wire can be shortened as far as possible.
Still another object of this invention is to provide a seat reclining apparatus capable off reducing thickness of each of a pair of base plates as far as possible, and capable of eliminating a welding step.